This application claims Paris Convention priority of Japanese Application Nos. 2000-142730 filed May 16, 2000 and 2000-142732 filed May 16, 2000, the complete disclosure of which are hereby incorporated by reference.
This invention relates to a device for collecting plasma or serum from blood vessel directly by drawing and filtering blood continuously.
Kind or concentration of blood components, such as metabolites, proteins, lipids, electrolytes, enzymes, antigens, and antibodies, is measured, in general, using a plasma or serum sample obtained by centrifuging whole blood. However, centrifuging takes labor and time. Particularly, centrifuging is unsuitable for an urgent case of measuring a small number of samples promptly and on site inspection, because of requiring a centrifuge and electricity. Thereupon, it has been investigated to separate plasma or serum from whole blood by filtration.
Several filtration methods using glass fiber filter have been known wherein whole blood is charged into glass fiber filter contained in a column from one side of the column and pressurized or sucked to obtain plasma or serum from the other side (Japanese Patent KOKOKU Nos. 44-14673, 5-52463, Japanese Patent KOKAI Nos. 2-208565, 4-208856).
However, practical filtration methods capable of obtaining an amount of plasma or serum from whole blood necessary for measuring by an automatic analyzer have not been developed except a part of items, such as blood sugar.
On the other hand, inventors belonging to the assignee of this application have developed a plasma or serum filtering unit comprising a filter element containing a combination of glass fiber filter and porous membrane and a baffle narrowing aperture of the filter element at an exit of a filtrate passage, with which plasma or serum can be separated effectively even from a small quantity of whole blood (U.S. Pat. No. 5,979,669).
Further, these inventors have developed a blood-filtering unit comprising a injection needle for drawing blood at an inlet of the blood-filtering unit and a filtrate receiver connected to an exit of a filtrate passage (U.S. Pat. No. 5,996,811).
But the unit was unsatisfactory for practical use in terms of uneasy operation or handling, since it required a sucking adaptor or syringe connected with the blood-filtering unit to collect and filter blood instantaneously.
Further, a device comprising a vacuum blood-drawing tube containing a injection needle at a front edge of it and accommodating a blood-filtering unit in it, a vacuum tube to suck in filtered serum or plasma, and a part with two injection needles connecting the vacuum blood-drawing tube and the vacuum tube has been developed to separate serum or plasma from whole blood (Japanese Patent KOKAI Nos. 4-208856, 5-93721, 5-188053).
But operation of this device is troublesome too. Because three injection needles contained in the device must be stung in correct order to connect four parts of the device.
An object of the invention is to provide a device with a simple structure capable of filtering blood to obtain plasma or serum for analysis.
The present inventors found out that the aforementioned problems are solved by one of plasma- or serum-collecting devices described bellow.
In a first embodiment, the shape of the device is adapted to a test tube. In this case, the well-balanced plasma- or serum-collecting device as a whole is obtained by utilizing an external suction equipment to draw and filter blood.
In a second embodiment, a blood-filtering unit is accommodated in a vacuum blood-drawing tube that comprises a partition wall between the blood-filtering unit and the bottom of the vacuum blood-drawing tube to build a vacuum room. In this case, a necessary volume of plasma or serum can be readily obtained by breaking the partition wall after blood to be filtered is drawn into the vacuum blood-drawing tube, since the blood is filtered with the blood-filtering unit by vacuum of the vacuum room.